1. Field of the Invention
The present invention relates to a technique of assessing whether a speech sound has actually been aurally comprehended or not. More specifically, the present invention relates to a speech discriminability assessment system for making an assessment of speech sound discriminability, which is needed for assessing the degree of “fitting” of a hearing aid or the like to provide a sound of appropriate loudness for each individual user by adjusting the amount of sound amplification. “Discriminability” is sometimes referred to as “discrimination score”.
2. Description of the Related Art
In recent years, for reasons such as the aging society, increased opportunities for listening to loud music for long hours, and so on, more and more people are suffering from presbycusis or hypacusia associated with acoustic traumas, and there is an increasing number of users who use hearing aids in order to aurally comprehend conversations in daily life more clearly.
Although the basic function of a hearing aid is sound amplification, the amount of sound amplification must be adjusted with respect to each user. For example, if the amount of amplification is insufficient, a sound pressure above the hearing threshold level will not be obtained, thus causing a problem in that the user cannot hear sounds. On the other hand, if more than a necessary amplification is applied, the UCL (uncomfortable level: a sound which is so loud that the user may feel uncomfortable) may be exceeded, in which case the user will feel uncomfortable. Therefore, before beginning use of a hearing aid, “fitting” is required for adjusting the amount of amplification so as to attain a sound of an appropriate loudness, which is neither too loud nor too soft, with respect to each user.
Fitting is generally performed based on each user's audiogram. An “audiogram” is a result of evaluating how a pure tone is “heard”: for example, a diagram in which, for each of a number of sounds of different frequencies, the smallest sound pressure level (decibel value) that the user can hear is plotted against frequency. Currently, however, a number of fitting methods are diversely present, and there is no one established fitting method that can determine an optimum amount of sound amplification with respect to any and every user for improving the conversational listening comprehension discriminability from his or her audiogram alone. Possible reasons are that an audiogram is not in one-to-one correspondence with a conversational listening comprehension ability, and that a person suffering from hypacusia has a narrow range of sound pressure that is felt to him or her as an appropriate loudness, for example.
Therefore, in order to evaluate the degree of fitting, a speech discriminability assessment for assessing whether a speech sound has actually been aurally comprehended or not is needed, and even after beginning use of a hearing aid, re-fitting must be performed by utilizing results of speech discriminability assessment.
As used herein, a “speech discriminability assessment” is an assessment of listening comprehension ability for assessing whether a monosyllabic speech sound has been aurally comprehended or not. A monosyllabic speech sound means either a single vowel or a combination of a consonant and a vowel (e.g., (a)”/(da)”/(shi)”). Since the purpose of wearing a hearing aid is aural distinction in conversations, assessment results of speech sound discriminability are regarded as important.
Conventionally, speech discriminability assessment has been performed through the following procedure. First, by using the 57S list (50 monosyllables) or the 67S list (20 monosyllables) proposed by the Japan Audiological Society, a user is allowed to hear a monosyllabic audio. Next, the user is asked to answer what he or she has aurally comprehended of the presented speech sound through oral explanation, writing, or other methods. Then, an evaluator matches the answers against the list in order to calculate a correctness rate.
However, in the aforementioned assessment method, the user is required to make answers via oral explanation or writing, and the evaluator needs to determine the correctness of the user's answers through manual labor. Thus, this test has presented a large burden on the user and the evaluator.
Therefore, for example, Japanese Laid-Open Patent Publication No. 9-038069 (Hereinafter, Patent Document 1) discloses a speech discriminability assessment method which, in order to reduce the burden of the evaluator, employs a personal computer (PC) to automatically perform correctness determination. Specifically, Patent Document 1 proposes a method in which monosyllabic audios are presented to a user by using a PC; the user is asked to answer by using a mouse or via pen-touch technique; the answers are received as inputs to the PC; and correctness determinations as to the presented audios and answer inputs are automatically made. Since answer inputs are received by using a mouse or via pen-touch technique, there is no need for the evaluator to analyze and distinguish the user's answers (which are given by oral explanation or writing), whereby the trouble of the evaluator is greatly reduced.
Moreover, for example, Japanese Laid-Open Patent Publication No. 6-114038 (Hereinafter, Patent Document 2) discloses a speech discriminability assessment method in which, after audio presentation, possible choices of speech sounds are presented in the form of text characters, thus reducing the user's burden of making answer inputs. In Patent Document 2, choices are limited to only a small number so that the relevant speech sound can be found among the small number of characters, whereby the user's trouble of finding the character is reduced. Also in Patent Document 2, a PC is used to receive answer inputs, thus reducing the evaluator's burden.
However, in the speech discriminability assessment methods described in Patent Document 1 and Patent Document 2, the user still needs to make answer inputs. Such an answer-inputting operation still exists and presents a burden on the user. In particular, it is presumably not easy for people suffering from hypacusia or elderly people who are unaccustomed to working on a PC to make answer inputs by using a mouse or a touch pen. There has also been a possibility that the wrong monosyllable matrix may be inadvertently selected through a manipulation mistake, in which case the speech sound discriminability may not be correctly evaluated.